1. Field of the Invention
The present invention relates to spring clips for attaching extensometers to specimens quickly and easily.
2. Description of the Prior Art
In the prior art, various methods of attaching extensometers to specimens have been advanced including rubber bands that are used for clipping extensometers directly to the specimen. Normally, extensometers carry some type of a specimen engaging point or knife edge that rests against the specimen under resilient load and when the test specimen is subjected to axial force, in particular, the extensometer arms will either tend to separate or move together as long as the knife edges or specimen contacting edges are kept against the specimen.
The Model 632.11 Axial Extensometer sold by MTS Sytems Corporation, Eden Prairie, Minn., is a typical extensometer using knife edges which engage the specimen, and in one form, namely the model 632.11B/C-45, which is a water cooled extensometer for high temperature chambers, a latch type clip is utilized for holding the extensometer on the specimen. This clip is a pivoting, relatively rigid wire, that is independently loaded with a coil spring mounted on the extensometer arms so that the knife edge on each extensometer arm is urged against the specimen when the latch is held in place by the force from a separate spring. The spring load for urging the knife edge against the specimen, is thus provided by a spring separate from the relatively rigid contact arm or clip that is used for attachment.
The clip is a multiple part assembly, and one of the problems that has arisen is making sure that the effective application line of the spring load against the knife edge is on a plane that passes through the axis of the specimen so that there isn't any moment or eccentric loading on the extensometer knife edges.